From fec4cf9109f4dab2f512fb2be7db1bcab8f3d23f Mon Sep 17 00:00:00 2001
From: John Benediktsson <mrjbq7@gmail.com>
Date: Mon, 3 Oct 2011 12:31:46 -0700
Subject: [PATCH] io.encodings.utf8: assume streams are largely ascii.

Results in 30% faster file-contents for test file and 7% faster benchmark.xml.
---
 core/io/encodings/encodings.factor |  8 ++---
 core/io/encodings/utf8/utf8.factor | 52 ++++++++++++++++--------------
 2 files changed, 31 insertions(+), 29 deletions(-)

diff --git a/core/io/encodings/encodings.factor b/core/io/encodings/encodings.factor
index 1b34b6aa8b..81037ca2df 100644
--- a/core/io/encodings/encodings.factor
+++ b/core/io/encodings/encodings.factor
@@ -78,10 +78,10 @@ M: decoder stream-read1
     ] keep ; inline
 
 : finish-read ( n/f string -- string/f )
-    {
-        { [ over 0 = ] [ 2drop f ] }
-        { [ over not ] [ nip ] }
-        [ swap head ]
+    swap {
+        { [ dup zero? ] [ 2drop f ] }
+        { [ dup not   ] [ drop ] }
+        [ head ]
     } cond ; inline
 
 M: decoder stream-read
diff --git a/core/io/encodings/utf8/utf8.factor b/core/io/encodings/utf8/utf8.factor
index 09e3dd5f4b..8fbc71e016 100644
--- a/core/io/encodings/utf8/utf8.factor
+++ b/core/io/encodings/utf8/utf8.factor
@@ -39,13 +39,14 @@ SINGLETON: utf8
     HEX: 10FFFF maximum-code-point ; inline
 
 : begin-utf8 ( stream byte -- stream char )
-    {
-        { [ dup -7 shift zero? ] [ ] }
-        { [ dup -5 shift BIN: 110 = ] [ double ] }
-        { [ dup -4 shift BIN: 1110 = ] [ triple ] }
-        { [ dup -3 shift BIN: 11110 = ] [ quadruple ] }
-        [ drop replacement-char ]
-    } cond ; inline
+    dup 127 > [
+        {
+            { [ dup -5 shift BIN: 110 = ] [ double ] }
+            { [ dup -4 shift BIN: 1110 = ] [ triple ] }
+            { [ dup -3 shift BIN: 11110 = ] [ quadruple ] }
+            [ drop replacement-char ]
+        } cond
+    ] when ; inline
 
 : decode-utf8 ( stream -- char/f )
     dup stream-read1 dup [ begin-utf8 ] when nip ; inline
@@ -59,24 +60,25 @@ M: utf8 decode-char
     BIN: 111111 bitand BIN: 10000000 bitor swap stream-write1 ; inline
 
 : char>utf8 ( char stream -- )
-    swap {
-        { [ dup -7 shift zero? ] [ swap stream-write1 ] }
-        { [ dup -11 shift zero? ] [
-            2dup -6 shift BIN: 11000000 bitor swap stream-write1
-            encoded
-        ] }
-        { [ dup -16 shift zero? ] [
-            2dup -12 shift BIN: 11100000 bitor swap stream-write1
-            2dup -6 shift encoded
-            encoded
-        ] }
-        [
-            2dup -18 shift BIN: 11110000 bitor swap stream-write1
-            2dup -12 shift encoded
-            2dup -6 shift encoded
-            encoded
-        ]
-    } cond ; inline
+    over 127 <= [ stream-write1 ] [
+        swap {
+            { [ dup -11 shift zero? ] [
+                2dup -6 shift BIN: 11000000 bitor swap stream-write1
+                encoded
+            ] }
+            { [ dup -16 shift zero? ] [
+                2dup -12 shift BIN: 11100000 bitor swap stream-write1
+                2dup -6 shift encoded
+                encoded
+            ] }
+            [
+                2dup -18 shift BIN: 11110000 bitor swap stream-write1
+                2dup -12 shift encoded
+                2dup -6 shift encoded
+                encoded
+            ]
+        } cond
+    ] if ; inline
 
 M: utf8 encode-char
     drop char>utf8 ;